Electron-positron plasma

Following the same procedure outlined for the cold plasma, we can specialize the system of (10.17) and (10.18) in Part I to the one-dimensional case with circular polarization and zero group velocity. The explicit forms of the relevant equations are given in [39], where RES in an electron-positron plasma were studied. Since the two species have equal masses and absolute values of charge, the plasma does not develop any charge separation for Te = Tp = T0 and so (j> 0. A single second-order nonlinear differential equa-... 

A kinetic approach to the study of one-dimensional RES in a hot plasma was developed in [44] and applied to RES in an electron-positron plasma [44], electron-ion plasma [45], and electron-positron-ion plasma [46]. A highly anisotropic particle distribution function for each plasma species j (where j = e for electrons and j = i for ions) was considered, with a finite constant... 

We can summarize the main results from the previous investigations in the following points (i) soliton solutions have been found under general conditions for an electron-positron plasma and by assuming quasi-neutrality in an electron-ion plasma (ii) sub-cycle nondrifting solitary waves represent an equilibrium in a multicomponent warm plasma that is, half-wavelengths of the EM radiation can be trapped inside a plasma density well (iii) the... 

Although positron plasmas can be considered to be systems containing many positrons, and as such technically fall within the scope of this section, we will not consider them here. Rather, we will concentrate on the theory of, and the possibilities of observing, assemblages of particles containing both positrons and electrons. These include the positronium molecule and a Bose-Einstein (BE) condensate of positronium atoms. 

A hot fluid model would be highly desirable for applications in astrophysics. As we have already mentioned, the formation of RES in the primordial plasma could be an important source of large-scale nonuniformities in density and temperature, which seeded the formation of galaxies and clusters of galaxies [4], In particular, it is conjectured that in the early universe matter was present in the form of a mixture of electrons, positrons and photons in thermal equilibrium at a temperature above me2. It is evident that the propagation of relativistic EM waves in such peculiar environment should be addressed in the framework of a hot-plasma model. 

If sufficient positrons can be confined, studies of particle transport within the plasma, etc., similar to those conducted with electrons can be carried out. It may be possible to use the enhanced detection possibilities afforded since positron-electron annihilations can be detected. An ultra-cold source of positrons would also have a variety of other applications.24 For example, it has been proposed to eject trapped positrons into a plasma as a diagnostic.25 Also, positrons initially in thermal equilibrium at 4.2K within a trap would form a pulsed positron beam of high brightness when accelerated out of the trap. 

The Doppler shifts of positron annihilations in the sample provide a more sensitive measure of this effect. The plasma treatment oxidizes the rather open structure of HSSQ. Oxygen atoms are included in the network. These have high momentum electrons in p-orbitals, which lower the sharpness of the annihilation line [22],... 

A gamma-ray line at 0.511 MeV results from the mutual annihilation of an electron and a positron, a particle-antiparticle pair. A number of radioactive decay chains (see Table I) result in the emission of a positron as a decay product, which will annihilate upon first encounter with an electron. Also of astrophysical importance is the production of electrons and positrons via the photon-photon pair-creation process. Such pair plasmas are found in the vicinity of compact objects, such as neutron stars and black holes, that are associated with heated accretion disks and relativistic flows and jets, within which particle acceleration is known to occur. Thus, relatively narrow lines of 0.511-MeV annihilation radiation are expected to arise in the interstellar medium through the decay of dispersed, nucleosynthetic radionuclides, while broadened, Doppler-shifted, and possibly time-variable lines may occur in the high-energy and dense environments associated with compact objects. 

---